aggression towards cats

Question
I have a year old female boxer (Roxie) who is very affectionate and has not shown any aggression towards adults, children or other dogs.  I also had a male boxer two years ago just show up in our yard and we kept him for two months  He was very aggressive towards our cats and my pug learned to chase the cats from him.  We had to find him a new home.  My present boxer did not bother the cats until this past August.  However now she chases the cats in the house and today cornered my big cat who is real skittish and generally hides under my bed even from me.  My husband was able to grab Roxie before she could injure the cat but the cat was so scared she urinated.  I don't know how to break her of this and my husband who loves the dog is threatening to find her a new home.   I should add that although I love the cats, they are more his than mine.
I suggested that maybe the cat would be happier in a home where she is the only animal but he wouldn't hear of giving her away.  Any suggestions on how to break Roxie of this behavior would be appreciated

Answer
The Boxer and Pug is exhibiting a learned behavior from the other Boxer that started the cat chasing.

I suggest getting a loud whistle or a horn of some kind (that makes a loud honking noise) and use it each and every time the two dogs chase a cat.

Then verbally reprimand them in a stern voice using easy to understand commands.

Be consistent and very soon, they will associate the bad behavior to the loud noise and stop.